Reciprocating floor conveyors have been used for several years in van bodies and in trailers for unloading cargo. These conveyor systems are widely used for transporting bulk material such as ground plant material for animal feed, saw dust, wood chips, bark and plant material for human consumption. The conveyor systems include a plurality of parallel floor slats. Each floor slat is mounted so that it can slide back and forth in a direction parallel to its long axis.
Several different drives and drive systems have been employed in reciprocating floor conveyors to reciprocate the floor slats back and forth. A commonly used drive system includes three hydraulic cylinders that move all the slats simultaneously to the rear toward a rear discharge, carrying the cargo with them. The first cylinder is connected to every third floor slat. The second cylinder is connected to all the floor slats that are adjacent to a common side of the floor slats attached to the first cylinder. The third cylinder is attached to the floor slats that are between the floor slats driven by the first cylinder and the floor slats driven by the second cylinder. The first, second and third cylinders are activated one at a time to move every third floor slat forward and away from the rear discharge without moving cargo forward. The floor slats do not carry cargo forward because the two-thirds of the floor slats that are stationary while one cylinder moves one-third of the floor slats forward, hold the cargo. The second cylinder moves the floor slats connected to it forward while the floor slats connected to the first and third cylinders remain stationary. The third cylinder then moves the floor slats connected to the third cylinder forward while the floor slats connected to the first and second cylinders remain stationary. The above procedure is then repeated to move the cargo through a rear discharge opening. The procedure continues to be repeated until all the cargo is discharged.
The floor slats that are currently used are made from metal such as aluminum. Aluminum slats cannot slide against each other because of galling unless every other floor slat is anodized. It is expensive to anodize aluminum. Anodizing aluminum floor slats would eliminate the galling problem but would not solve the temperature expansion problem. Aluminum expands with temperature increases and contracts with temperature decreases. To accommodate aluminum thermal contraction and expansion, small gaps are provided between the floor slats of reciprocating floor conveyors. These gaps eliminate the thermal expansion problem as well as the galling problem.
The gaps between adjacent floor slats in reciprocating floor conveyors create two problems. One of the problems is loss of cargo. This is not a serious problem if the cargo is non-toxic and inexpensive. Loss of cargo is a serious problem however if the cargo is a toxic material or if the cargo is expensive. Another problem is cargo contamination. Cargo can be contaminated by material on a road surface that is thrown upwardly by vehicle wheels and passes through slots between floor slats. The cargo contamination problem is extremely serious if the cargo is for human or even animal consumption.
Two basic types of solutions to the problems caused by spaces between floor slats have been tried. One of the solutions is to catch material that passes between the floor slats in either direction. This solution adds weight and expense to reciprocating floor conveyor systems. Catching material that passes down between two slats also adds disposal problems if it is necessary to dispose of the material that is caught. Seals between floor slats have been the preferred solution to the problems. Seals between the slats can virtually eliminate cargo loss as well as cargo contamination. Seals between reciprocating floor slats have relatively short useful lives, take time to replace and are expensive. These seals are generally resilient and rely upon their resilience to maintain sealing contact. Seals that can be inflated have also been tried. Inflatable seals are deflated during conveying operations. There are many solid and semi-solid caustic materials which can be transported on and unloaded by reciprocating floor conveyors. Unfortunately aluminum floor slats have unacceptably short useful lives when they are in direct contact with caustic materials. Coatings on the aluminum floor slats extend their useful life somewhat. Unfortunately the sliding contact between cargo and floor slats that occurs during cargo unloading tends to remove coatings within a short period of time.